Larger brain size doesn't guarantee higher IQ

London: Men may have larger brains than women but that does not make them more intelligent than the members of the fair sex, says a new study that found a very weak association between brain size and IQ.

"Brain volume plays only a minor role in explaining IQ test performance in humans,” said one of the researchers Jakob Pietschnig from the Institute of Applied Psychology of University of Vienna in Austria.

The findings are based on data from over 8,000 participants.

"Rather, brain structure and integrity appear to be more important as a biological foundation of IQ, whilst brain size works as one of many compensatory mechanisms of cognitive functions," Pietschnig noted.

For instance, differences in brain size between men and women are well-established, yielding larger brains of men compared to women.

However, there are no differences in global IQ test performance between men and women, the researchers pointed out.

They noted that the importance of brain structure compared to brain volume becomes already evident when comparing different species.

When considering absolute brain size, the sperm whale weighs in with the largest central nervous system.

Similar results emerge when considering other aspects of species anatomy: Homo sapiens never appears at the top at the list, as would be expected.

Rather, differences in brain structure appear to be mainly responsible for between-species differences in cognitive performance, the study said.

Another example are individuals with megalencephaly syndrome (enlarged brain volume) who typically show lower IQ test performance than the average population.

"Therefore, structural aspects appear to be more important for cognitive performance within humans as well," Pietschnig noted.

The findings appeared in the journal Neuroscience and Biobehavioral Reviews.